The accountant who gave the wrong envelope to the presenters of the Academy Award for best picture was at the centre of a probe over how the meticulous procedure went disastrously awry, handing victory to La La Land before declaring Moonlight the real winner.

In a gaffe on Sunday that stunned the Dolby Theatre crowd in Hollywood and a television audience worldwide, presenters Warren Beatty and Faye Dunaway read from the wrong envelope for the movie industry’s top award.

The Wall Street Journal and celebrity website TMZ.com reported on Monday that Brian Cullinan, one of the PricewaterhouseCoopers accountants responsible for handing out the sealed envelopes on Sunday had been posting on Twitter minutes before the mix-up.

A backstage photo of best actress winner Emma Stone was posted on Cullinan’s Twitter account. It was later deleted but was still viewable on Monday on a cached archive of the page.

PricewaterhouseCoopers US chairman Tim Ryan confirmed to USA Today on Monday that Cullinan was the person who handed the envelope to Beatty.

PwC did not respond to requests for comment on Cullinan’s tweet, nor his role in the envelope fiasco. Cullinan could not immediately be reached for comment.

The mistake was not rectified until the La La Land cast and producers were on stage giving their acceptance speeches. It was left to the musical’s producer, Jordan Horowitz, to put things right.

“Guys, guys, I’m sorry. No. There’s a mistake,” Horowitz said. “‘Moonlight, you guys won best picture. This is not a joke.”

It took PricewaterhouseCoopers, which has been overseeing Academy Awards balloting for 83 years, three hours to issue a statement confirming that Beatty and Dunaway “had mistakenly been given the wrong category envelope.”

The Academy of Motion Picture Arts and Sciences, which organises the Oscars, has made no comment.

An embarrassed Beatty carried the envelope in his hand to the glitzy Governor’s Ball after the show, with the writing clearly saying “actress in a leading role”, evidence, he said, that the blunder did not belong to him or Dunaway. La La Land star Stone had been awarded that Oscar moments before.

Brand management experts said it could take years for PricewaterhouseCoopers (PwC) to recover.

“This is not advanced math. PwC had to get the right name in the right envelope and get it to the right person,” said Tim Calkins, a marketing professor at Northwestern University, calling the blunder a “bit of a branding tragedy.”

Under a tried and tested PwC procedure, just two accountants know the names of the 24 winners after their names are placed in two sets of sealed envelopes. The two accountants also memorise the winning names.

Tradition has it that the envelopes are taken separately in two briefcases to the Academy Awards venue. The two accountants - in this case Cullinan and Martha Ruiz - are driven there separately in case an accident or traffic should befall them.

The pair then stand off stage at opposite sides and hand envelopes to the respective presenters as each category is announced.

Last week, Cullinan told the Huffington Post that the procedure for dealing with the hand-off of an incorrect envelope, other than signaling to a stage manager, was unclear.

“It’s so unlikely,” Cullinan told the Huffington Post.

Anthony Sabino, a law professor at St John’s University in New York, said that although precious minutes passed, the error was corrected quickly.

“It’s not as if we woke up this morning, or if it had been uncovered after the telecast was over. That would have really have been a black eye,” Sabino said.

Sabino said that compared to accounting fraud at other companies in the past, “this incident diminished vastly to a vanishing point.”

The Moonlight filmmakers were gracious about the error.

Director Barry Jenkins told reporters back stage that he was given no immediate explanation for the mix-up but that “it made a very special feeling even more special, but not in the way I expected.”

“Please write this down: The folks from La La Land were so gracious,” Jenkins added.

How the fiasco unfolded

— The consulting firm PwC, PricewaterhouseCoopers, tabulates the winners based on ballots cast by the academy’s 6,687 voting members.

— Two accountants are tasked with bringing the final results, inside sealed envelopes, to the Oscars ceremony. They are the people carrying briefcases on the red carpet, flanked by police protection. Each briefcase contains an identical set of envelopes for the show’s 24 categories. The accountants also memorise the winners.

— The two accountants are ostensibly the only people who know the winners before they are announced live on TV.

— During the telecast, the two briefcase-toting accountants are stationed in the Dolby Theatre wings, one stage left and one stage right.

— Most presenters enter stage right. They come backstage a few minutes ahead of time, and the accountant hands them their category’s envelope just before they walk onstage. The sealed envelope with the winner’s name inside is opened live onstage.